News Release Number: STScI-2011-02

NASA's Hubble Finds that Puny Stars Pack a Big Punch

January 10, 2011: A survey of more than 200,000 stars in our Milky Way galaxy has unveiled the sometimes petulant behavior of tiny dwarf stars. These stars, which are smaller than the Sun, can unleash
powerful eruptions called flares that may release the energy of
more than 100 million atomic bombs. Red dwarfs are the most
abundant stars in our universe and are presumably hosts to
numerous planets. However, their erratic behavior could make
life unpleasant, if not impossible, for many alien worlds. The
flares the stars unleash would blast any planets orbiting them
with ultraviolet light, bursts of X-rays, and a gush of charged
particles called a stellar wind.

Studying the light from 215,000 dwarfs collected in
observations by NASA's Hubble Space Telescope, astronomers
found 100 stellar flares. The observations, taken over a seven-day period, constitute the largest continuous monitoring of red
dwarf stars ever undertaken. The illustration shows a red dwarf
star unleashing a powerful flare. A hypothetical planet is in the
foreground.